The terrorist attacks of September 11, 2001, provide a tragic but unique opportunity to study risk factors for the emergence of PTSD symptoms in vulnerable individuals as a result of significant but indirect trauma. The research literature has begun to characterize many of the individual vulnerability and environmental factors for the emergence of PTSD. However, information on these putative vulnerability factors is limited by the general unavailability of pre-trauma variables in affected individuals. In addition, much of the available information is specific to the emergence of PTSD resulting from the direct exposure to a trauma. We propose to examine this issue with a study to be embedded within the ongoing evaluation of an outpatient population of bipolar patients, the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). STEP-BD is a multi-center, longitudinal study that provides an unprecedented opportunity to examine the emergence and consequences of PTSD and associated symptoms following the September 11th attacks. STEP-BD offers to the study of PTSD the rare opportunity to use a large data set that richly characterizes the functioning of a vulnerable population prior to the onset of trauma, and has in place a study team and procedures for monitoring the psychiatric outcomes for these individuals over time. Accordingly, we are proposing additional assessment protocols to allow analysis of the impact of indirect exposure to the September 11th attacks, on 260 individuals at two of the largest STEP sites. By collecting information on the symptomatic response to the September 11th attacks, this proposed study can provide an especially comprehensive assessment of pre- event risk factors for PTSD in response to a uniform stressor and its effects on the subsequent course of illness.